Impact responsive signal pick-up



July 26, 1966 wm lss 3,263,039

IMPACT RESPONSIVE SIGNAL PICK-UP Filed May 26, 1964 FIG; 3.

II I C140 0 13a 13 I52 15 Mm Y W I54 I55 I56 ATTORNEYS.

United States Patent 3,263,039 IMPACT RESPONSIVE SIGNAL PICK-UP George Wintriss, Carversville, Pa., assignor to Industriomcs Controls, Inc.,New York, N.Y., a corporation of New York Filed May 26, 1964, Ser. No. 370,276 12 Claims. (Cl. 200-61.45)

This invention relates to apparatus for producing signal pulses in an electric control circuit in response to an impact against an abutment surface.

One of the ways in which control mechanism has been used to determine malfunctioning of automatic machines has been by projecting delivered work pieces from the machine against detector means, and to actuate the control mechanism in any cycle where there is no work piece delivered at the time in the cycle when a work piece should be delivered. Apparatus has been used for picking up the sound of the work piece striking the detector melans; and the sound signal has been used as a control pu se.

Experience has shown, however, that sonic pickups are not sufiiciently rugged to withstand long, repeated stress of impact or vibration, and such controls eventually fail or become unreliable. It is an object of this invention to provide an improved apparatus for producing useful control signals in response to the cyclic delivery of work pieces by an automatic machine.

It is a more specific object of the invention to provide an electric circuit including an inertia element in the chamber of a housing in which the inertia element touches a relatively fixed contact in the housing for a normally closed circuit, or is spaced a short distance away from the fixed contact for a normally open circuit. With either construction, the inertia element moves with respect to the fixed contact to change the condition of the circuit for a brief interval in response to impact of a work piece with an abutment surface on the outside of the housing.

The invention includes means for converting short, momentary makes or breaks of the electric circuit into useful pulses in a control circuit; and the construction is simple and rugged so that it operates indefinitely with reliability.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views:

FIGURE 1 is a sectional view showing a preferred embodiment of the invention;

FIGURE 2 is a transverse sectional view taken on the line 22 of FIGURE 1;

FIGURE 3 is a view similar to FIGURE 1 but showing a modified form of the invention;

FIGURE 4 is another view similar to FIGURES 1 and 3 but showing still another modified form of the invention;

FIGURE 5 is a wiring diagram for a portion of a circuit for this invention;

FIGURE 5A is a diagram showing the variations in the voltage in the circuit shown in FIGURE 5;

FIGURE 6 is a wiring diagram for a portion of the circuit used with a modified form of the invention shown in FIGURE 4;

FIGURE 6A is a diagram showing voltage variation with the circuit shown in FIGURE 6; and

FIGURE 7 is another wiring diagram for other portious of the circuit used with this invention.

The impact detector shown in FIGURE 1 includes a cup 10 having a bottom 12 and side walls 14. In the preferred construction the cup is of circular cross section. The inside of the cup 10 is made with a number of I different diameters and the diameter changes abruptly to form shoulders 16; 17; 18; 19; and 20. The illustrated construction has the cup 10 made of metal, preferably aluminum, and constructed with the bottom 12 and side walls 14 of one-piece construction.

The upper end of the cup 10 is closed by a plug 24 which seats against the shoulder 19 and which has an upper flange that seats against the shoulder 20. In order to hold the plug 24 securely in the cup 10, upper edge portions 26 of the side wall of the cup are bent inwardly to grip the tapered peripheral portion of the plug 24. Before the parts are inserted into the cup 10 and before the plug 24 is permanently put in place, the upper edge portions 26 of the cup extend in the direction indicated by dotted lines in FIGURE 1.

The plug 24 holds a cylindrical block of insulation 30 downward against a metal block 32. This metal block 32 seats on a washer 34 which is made of electrical insulating material for preventing actual contact of the metal block 32 with the shoulder 17, but the washer 34 is supported by the shoulder 17 and the metal block 32 is clamped against the Washer 34 by pressure of the insulation 30.

i The metal block 32 is also insulated from the cup 10 by a sleeve 38 of electrical insulating material. The top of the block 32 is electrically connected by a helical conductor 40 to a contact 41 at the end of a conductor 42 which has insulation 44 surrounding it where it passes through the plug 24. The lower end of the conductor or cable 42 is insulated from the plug 24 by a grommet or bushing 48 made of electrical insulating material. Thus the conductor 42 in the insulated cable is electrically connected to the metal block 32 which serves as a fixed electrical contact in the cup 10.

' The space within the cup 10, below the plug 24, constitutes a chamber enclosed by the cup 10 as a housing. The insulation 30 and the metal block 32 are fixed in this chamber but there is another metal block constituting an inertia element 54 located in the portion of the chamber below the shoulder 17. This inertia element 54 has a height dimension slightly less than the distance from the bottom of the metal block 32 to the shoulder 16; and the inertia element 54 has a limited reciprocating movement between the bottom of the block '32 and the shoulder 16. This limited movement provides a short stroke for the inertia element 54; and there is a spring 56 in the lowermost part of the cup 10 below the shoulder 16, for urging the inertia element 54 into constant contact with the metal block 32. The inertia element 54 may be said to move as a piston in the portion of the chamber between the shoulders 16 and 17 the side walls of the chamber providing the guidance for the inertia element 54. In the preferred construction, the peripheral portion of the inertia element 54 is higher than the remainder of this element and is the part which actually contacts with the bottom face of the plug 32, but other face contours can be used.

The spring 56 is made of metal and conducts electricity so that the spring 56 in addition to providing a bias for the inertia element 54 towardthe block 32, also provides a good electrical path between the inertia element '54 and the housing or cup 10. One side of the circuit,

which the detector controls, is connected with the conductor 42, and the other side is connected to a conductor 60 which is secured to the outside wall of the cup 10 by spot welding or any other suitable manner.

The outside surface of the bottom of the cup 10 can be used as anabutment surface, if desired; but in the preferred construction of the invention there is a plate 64 connected to the bottom of the cup 10 by screws 66 located at angularly spaced regions around the circumference of the cup 10. This plate 64 may be made of material, which is harder than that used for the cup 10; for example, steel, and the outside surface of the steel plate 64 provides an abutment surface which is more resistant to wear than would be the case with the aluminum bottom of the cup 10.

In order to prevent moisture, fumes, or other fluid from gaining access to the chamber within the housing or cup 10, there is a sealing ring 68 located in a recess around the periphery of the insulation 30 and contacting with the side wall of the cup between the shoulders 18 and 19. Various other means can be used for sealing the chamber against moisture.

When a work piece or other element strikes the abutment surface of the plate 64, the momentum of the piece causes a shock to be transmitted to the housing or cup 10 and this shock causes the block 32 and the other parts of the cup or housing assembly to jump away from the inertia element 54, or vice versa, depending upon how the application of force is considered to be applied. In any event, the shock causes the metal block 32 and the inertia element 54 to move apart, or to reduce their pressure against one another, depending upon the force of the shock.

If the impact merely causes a reduction in the pressure between the touching areas of the metal block 32 and the inertia element 54, then there will be a reduction in the voltage because of an increased voltage drop across the areas of contact of the block 32 and inertia element 54; but if the shock is sufficient to cause a complete breaking of the contact between the metal block 32 and the inertia element 54, then the circuit is completely opened, and maximum voltage variations obtained. The effect of making and breaking the electric contacts in the chamber in the housing will be considered more fully in connection with FIGURES and 6.

The impact required to separate the inertia element 54 from the fixed contact block 32 depends upon a number of factors. One is the mass of the plate 64, the housing or cup and the other parts that are assembled with the cup 10. Another factor is the mass of the inertia element 54. The spring 56 is a factor but is such a small one that it can be ignored. This spring 56 is used only for the purpose of maintaining an intimate contact of the inertia element 54 with the fixed element block 32 and for conveying electricity from the cup 10 to the inertia element 54. In constructing the invention, it is necessary for the engineer to know what magnitude of impact is to be used to operate the detector. The design is, of course, for the smallest impact which will operate the detector, and any larger impacts will of course be effective. For use on machines manufacturing relatively small and light work pieces, this invention is designed to react to a minimum kinetic energy of .0006 erg, and to Withstand an unlimited amount of impact above this minimum.

This minimum energy corresponds to the impact caused by the free fall over the distance of three inches of a quarter inch diameter steel ball, and it has been found to approximate the impact of an average size part as ejected from a metal stamping and forming machine. Such a part has a mass of approximately .22 gram.

Experience has shown that with work pieces having a mass of approximately .22 gram, the inertia element 54 should have a mass of approximately twice that of the work piece, that is, .44 gram; and the plate housing assembly should have a mass approximately twelve times as great as that of the work piece, that is 2.64 grams. These values are approximate and there is some variation in the velocity of the impact which makes it undesirable to compute the ratios too closely.

If it is desired to have the impact detector less sensitive, because of vibration or other conditions, and the impacts are of sufficient magnitude to substantially exceed .0006 erg, then the mass of the inertia element 54 and the mass of the plate-housing assembly can be increased proportionately for the equivalent larger mass of the work piece. It will be understood that these numerical values are given by way of illustration.

FIGURE 3 shows a modified construction in which the plate for the impact surface is omitted for simpler illustration and other parts of theassembly which correspond to those of FIGURE 1 are iridicated'by the same reference character with a prime appended.

The essential difference between the construction shown in FIGURE 3 arid that shown in FIGURE 1 is that the inertia element 54 is held against a fixed metal block 72 by magnetic attraction. The metal block 72 is preferably a permanent magnet and is illustrated as a horseshoe type. Since no spring force under the inertia element 54 is required to maintain contact of the inertia element 54' and the magnetic block 72, it is sufficient to merely have a helical flexible conductor 74 for maintaining the electrical path from the, inertia element 54 to the metal of the cup 10. This conductor 74 can be secured to the bottom of the inertia element 54 and need exert no spring action, or it can be a very light spring which is not sufiicient to lift the inertia element 54' but which is sufiicient to maintain the ends of the conductor 74 in contact with the bottom surface of the inertia element 54 and the confronting surface at the bottom of the chamber enclosed in the housing or cup 10'.

The stroke of the inertia element 54' is short enough, in proportion to the flux of the magnetic block 72, to enable the magnetic attraction to return the inertia element 54' to contact with the magnetic block 72 whenever the contact is broken by an impact which jars the assembly with sufficient force to separate the inertia element 54' from the magnet 72. Actually the pull of a magnet varies so steeply as the air gap decreases that the impact detector of FIGURE 3 is not as sensitive as the impact detector shown in FIGURE 1; and it cannot be made as sensitive for long periods of use because of the variations which necessarily occur in magnetic strength and because of the substantial reduction in the circtliit restoring force if the magnetic flux is made very Wea The electric circuit from the magnetic block 72 to the insulated conductor 42 is through a conductor 76 which differs slightly in construction from the conductor 40 of FIGURE 1, but which serves the same purpose.

FIGURE 4 shows another modified form of the invention. Whereas the constructions shown in FIGURES 1 and 3 are normally closed circuits which open only in response to a substantial impact, the apparatus shown in FIGURE 4 provides a normally open circuit which closes only when there is a substantial impact against the hous- 111g.

In FIGURE 4 a cup 80 has a cylindrical metal block 82 in the lower end of the chamber enclosed by the housingor cup 80 and there is a conductor spring 84 for providing a strong contact pressure for the passage of electricity from the metal block 82 to the metal of the cup 80. There is an electrically insulating Washer 86 on top of the metal block 82 and this washer 86 supports a metal sleeve 88 having an inside diameter slightly less than that of the washer 86. An outer. sleeve 90 of electrical insulating material surrounds the sleeve 88 and insulates the sleeve 88 from the metal of the housing or cup 80.

An inertia element 92, comprising a metal block slides up and down in the sleeve 88 as a guide and there is a center opening through the inertia element 92 for passage of a spring 94 which is connected at its lower end to the inertia element 92 by a cross bar 96, and which is connected at its upper end to a clamping block 98 by a cross pin 100. This spring 94 holds the inertia element 92 up against the bottom face of the clamping block 98 except at such times as the inertia element is moved away from the clamping block by an impact which suddenly jars the assembly.

Any sudden blow which has a component of force in an axial direction; that is, in the direction in which the inertia element 92 moves, causes this inertia element 92 to spring away from the clamping block 98. If the shock is of suflicient magnitude, the motion of the inertia element 92 carries it into contact with the metal block 82 and closes an electric circuit through the apparatus.

The clamping block 98 is held down against the top of the metal sleeve 88 by a block of insulation 104 which corresponds to the insulation 30 of FIGURE 1; and this insulation 104 is held against the clamping block 98 by an upper plug 186 corresponding to the plug 24 of FIG- URE 1 and held in the cup' 80 by turned in upper edges 108 at the top of the cup.

The chamber within the cup 80 is sealed against moisture by a sealing ring 110 and the circuit from the inertia element 92 and spring 94. is continued by a flexible conductor 112 to an electric cable 114 extending through the metal plug 106 and insulated therefrom by insulation 116, this construction being similar to that described already in connection with FIGURES 1 and 3.

The operation of the apparatus shown in FIGURE 4 is not essentially different in principle from that of FIG- URES 1 and 2. The forces resulting from the elasticity of the parts cause the inertia element to spring away from the face with which it is in contact when there is a sharp blow transmitted through the housing with a component in an axial direction which is the same as the direction in which the inertia element is free to move. Experience shows that the components of force transmitted by a shock against the outside of the housing or cup are complicated. Whereas it is evident that the inertia element and the element with which it contacts will not move with respect to one another unless there is a force in the direction in which they can move away from one another, the forces involved are forces of elasticity in the parts of the assembly and impacts directed against the side of the cup, instead of against the end of the cup, also set up components of force resulting in the elasticity of the parts which move the inertia element with respect to the fixed contact.

FIGURE 5 shows a circuit in which power from a terminal 126 is supplied through resistors 128 and 129 to a terminal 130 which is for connection with .apparatus in which a detected pulse is to be used. A switch 132 is connected from the circuit, between the resistors 128 and 129, to ground. This switch 132 is normally closed. It corresponds to the embodiments of the invention shown in FIGURES 1 and 2 where the inertia element maintains the circuit closed except when interrupted by a shock.

FIGURE 5a is a diagram showing the voltage across the switch 132.

When the switch is closed the voltage across the switch is zero and no power is supplied to the terminal 130 because the switch 132 short circuits the circuit to ground. When ,an impact produces a shock which opens the switch 132 momentarily, the voltage drop across the switch suddently jumps up as indicated by the voltage rise 134 in FIGURE 5a, the value reaching that of the supply terminal 126. The circuit is promptly closed by the bias which urges the inertia element toward the fixed element and by the elastic forces involved in the apparatus, and this causes the voltage drop across the switch 132 to dropagain to zero.

The elastic forces produced by the shock are involved with reaction forces or vibration so that the contacting parts tend to separate again and they may separate completely so as to produce another wave equal to the voltage rise 134 but unless the shock is quite substantial, the next voltage rise will produce a wave 136 which is not quite as high as the voltage rise 134 indicating that the parts do not completely separate but merely lighten their contact with one another. Similarly there will be other elastic oscillations which will produce variations in pressure of thewcontact surfaces of the switch 132 resulting in other waves 138, 139 and 140, the waves being attenuated so that after a reasonable number of waves th voltage drop will again become constant along the zero line. The waves shown in FIGURE 5a are of variable frequency and duration to indicate the irregularity of the voltage variations which are produced by the chatter of the switch contacts in the switch 132.

FIGURE 6 shows another circuit having terminals at its opposite ends indicated by the reference characters 136 and 138. There are a number of resistors 141, 142, and 143 connected in series between the terminals 136 and 138. A conductor is connected with the circuit between the resistors 142 and 143 and this conductor 145 leads to a terminal 130' to which is to be connected the apparatus which will use the pulse supplied by the impact device of this invention. A switch 148 is connected with the circuit between the resistors 141 and 142 and the other side of the switch is grounded so that when the switch 148 is closed, the voltage drop of the circuit is reduced and there is less voltage supplied to the terminal130'.

The switch 148 corresponds to the impulse detector shown in FIGURE 4. When the switch 148 is normally open, there is a voltage indicated by the voltage line 150 across the switch 148. When the switch 148 closes, there is a sudden drop in the voltage across the switch as indicated by the wave 152. This maximum variation in voltage results from a firm contact between the contacts of the switch 148 with no substantial voltage drop across the switch contacts.

With the secondary, attenuated vibration which follows the first making of the circuit, the contacts of the switch 148 come together with less fonce on subsequent movements and there is a progressively greater drop between the contacts because of the lack of firm pressure. This results in subsequent voltage waves 154, 155, 156, 157 and 158, each of which is of less amplitude than the one ahead of it, as shown in FIGURE 6A.

Because of the extremely short duration of the pulses produced by apparatus of FIGURES 1, 3 and 4, most electrical control devices are unable to respond to such signals. It is desirable therefore to provide additional circuitry for increasing the effective length of the pulses so that they can be used for operating control equipment.

FIGURE 7 shows a circuit with electrical elements for increasing the effective length of a voltage pulse supplied to the terminal 130. This terminal is connected by a conductor to a transistor 172 which is connected in a circuit so as to be normally conducting. The transistor 172 is connected with another transistor 174 by a conductor 176 and the transistor 174 is normally non-conducting. Power for the circuit of FIGURE 7 is supplied from a terminal 178 and only the pulses for triggering the transistor operation are supplied through the terminal 130 from the impact detection device of this invention.

The circuit shown in FIGURE 7 is an inverter and it produces a signal only when a break occurs in the supply of current at the terminal 130. The operation of the transistors then energizes a coil 180 of a reed relay indicated generally by the reference character 182; and energizing of the relay coil 180 closes contacts 184 of the reed relay so as to establish .a circuit between the output terminals 186 of the relay.

It is this switch 184 which acts as the control circuit in response to the detection of impacts by the impact detection apparatus of this invention.

The preferred embodiment of the invention has been illustrated and described, but changes and modifications can be made, and some features can be used in different combinations without departing from the invention as defined in the claims.

What is claimed is:

1. A magnetic impact detector comprising a housing enclosing a chamber, a ferrous metal contact element within the chamber, a free-sliding inertia element within the housing and also made of ferrous metal, the inertia element having a face confronting a face of the contact element and movable toward and from said contact element in response to impacts that jar the housing, said inertia element fitting in the chamber and being guided by the wall of the chamber during its movement toward and from the contact element, and the confronting faces of the inertia element and contact element touching one another at substantially radial distances from the centers of said faces and at least one of the elements being magnetic for holding the elements in contact with one another and for restoring them to contact when the inertia element is caused to move away from the other element in response to jarring of the housing by impact of the element against the housing.

2. A non-magnetic impact detector comprising a housing enclosing a chamber, two electric contact elements in the housing and having confronting faces and neither of which is a magnet, one of the contact elements being a block that is movable toward and from the other contact in response to jarring of the housing by impact of an element against the outside of the housing, said block having a free-sliding fit in the chamber and being guided by the wall of the chamber during its movement toward and from the other contact, and the confronting faces of the contacts touching one another at substantial radial distances from the centers of said faces and means normally urging the sliding block into contact with the other contact element, said means comprising a spring.

3. Apparatus for detecting impact of an element with an impact surface including a housing enclosing a chamber, two electric contacts in the housing including a first contact and a second contact, the latter being movable axially at the housing toward and from the first contact, each of said contacts being part of an electric circuit through the apparatus, an inertia element freely movable in the chamber and at least a part of which constitutes the second electric contact, and a plate attached to the outside of the housing at one end of the longitudinal axis of the housing and in position to transmit shocks from impact of an element, against the plate, in a direction having at least a component in the same direction as the movement of the inertia element with respect to the first contact.

4. The apparatus described in claim 3 characterized by the inertia element being a free-sliding block in the chamber guided by the side wall of the chamber, at least the portion of the chamber that guides the inertia element being made of electric insulating material, and a flexible electric conductor connected with one end of the inertia element and with the electric circuit that is made and broken by said electric contacts.

5. The apparatus described in claim 3 characterized by the inertia element being a block that reciprocates through a short stroke toward and from the first contact, and yieldable means holding the block at one end of its stroke to give the apparatus a bias toward one circuit condition.

6. The apparatus described in claim 5 characterized by the yielding means being a spring.

7. The apparatus described in claim 5 characterized by the yielding means being a magnet.

8. An impact detector including a housing enclosing a chamber, a relatively fixed electric contact at one end of the chamber, an inertia element in the chamber and comprising a free-floating element having a contact face confronting a face of the relatively fixed contact movable toward and from one end of the chamber, said free-floating element being guided by the side wall of the chamber,

the confronting faces of the relatively fixed contact and the free-floating element touching one another at locations at substantial distances radially outward from the centers of said faces, yieldable means for holding one end of the inertia element against said fixed contact, a flexible electrical conductor connected with the inertia element and leading therefrom to an external circuit, and an abutment surface on the outside of the housing at a location to jar the housing and inertia element momentarily out of contact with one another when the abutment surface is subjected to substantial impact.

9. The impact detector described in claim 8 characterized by the inertia element having a circular transverse cross section, and the chamber having a cylindrical portion in which the inertia element slides freely as a piston, the flexible electrical conductor being a wire having a number of coils for imparting the flexibility to said electrical conductor.

10. The impact detector described in claim 9 characterized by the abutment surface being at one end of the housing in line with the cylindrical axis of the chamber and at the end of the inertia element remote from the fixed contact whereby impact jars the housing and the fixed contact away from the inertia element to break the electric circuit.

11. An impact detector including a cup having a bottom and side walls of integral construction, the cup having an inside surface that increases in diameter at several shoulders spaced axially along the height of the cup, an inertia element in the lower part of the cup and including a block slideable in the cup with the sides of the cup as a guide, a fixed electric contact including another block of larger diameter than the inertia element and supported by the housing above one of the shoulders thereof, means closing the upper end of the cup including a block of insulation above the fixed element and a plug fitting into the upper part of the cup above the last shoulder and supported by said last shoulder, means sealing the lower part of the inside of the cup from entrance of moisture therein, and electrical conductors in electric connection with the fixed element and the slideable block, respectively'.

12. The impact detector described in claim 11 characterized by the cup being made of metal and the bottom and side of the cup being of one-piece construction, an impact plate connected by a screw threaded connec tion with the bottom of the cup on the outside thereof, a spring in the cup under the slideable block and in a portion of the cup that is of less diameter than the sliding block, said spring urging the sliding block upward into contact with the fixed block above it, an insulated electric conductor extending from the fixed block on the side remote from the sliding block and through the insulation and plug to the outside of the cup, all of the parts within the cup being retained therein by a top edge portion of the sides of the cup extending inward over the peripheral portion of the upper end of the plug.

References Cited by the Examiner UNITED STATES PATENTS 12/1956 Lin 735l7 X 3/1961 Brueggeman etal. 2006l.53 X

OTHER REFERENCES Fraser et al.: Abreviature of application Serial No. 560,068, published Sept. 6, 1949, 626 O.G. 285. 

1. A MAGNETIC IMPACT DETECTOR COMPRISING A HOUSING ENCLOSING A CHAMBER, A FERROUS METAL CONTACT ELEMENT WITHIN THE CHAMBER, A FREE-SLIDING INERTIA ELEMENT WITHIN THE HOUSING AND ALSO MADE OF FERROUS METAL, THE INERTIA ELEMENT HAVING A FACE CONFRONTING A FACE OF THE CONTACT ELEMENT AND MOVABLE TOWARD AND FROM SAID CONTACT ELEMENT IN RESPONSE TO IMPACTS THAT JAR THE HOUSING, SAID INERTIA ELEMENT FITTING IN THE CHAMBER AND BEING GUIDED BY THE WALL OF THE CHAMBER DURING ITS MOVEMENT TOWARD AND FROM THE CONTACT ELEMENT, AND THE CONFRONTING FACES OF THE INERTIA ELEMENT AND CONTACT ELEMENT TOUCHING ONE ANOTHER AT SUBSTANTIALLY RADIAL DISTANCES FROM THE CENTERS OF SAID FACES AND AT LEAST ONE OF THE ELEMENTS BEING MAGNETIC FOR HOLDING THE ELEMENTS IN CONTACT WITH ONE ANOTHER AND FOR RESTORING THEM TO CONTACT WHEN THE INERTIA ELEMENT IS CAUSED TO MOVE AWAY FROM THE OTHER ELEMENT IN RESPONSE TO JARRING OF THE HOUSING BY IMPACT OF THE ELEMENT AGAINST THE HOUSING. 